I dislike AFA cases full stop as you can't handle the card if needed, cannot support the bubble if you ever need to post or transport it, and cannot easily change cases if it gets scratched or damaged, plus I object to paying someone else to tell me their highly subjective and certainly no more expert than anyone else's opinion about how good something that I already own and can see with my own eyes is! Having said that, I love GW acrylic cases, as they display MOCs beautifully, but can be opened if needed, thus countering all of the objections listed above for AFA cases.
In this instance, if you're going to display Mr Fett and have no other reason for opening the AFA case, then I agree that leaving it alone is the most sensible option, in case you damage the card when opening the case (although if you're careful, you really shouldn't, but anyway...). You have a great display piece, and if you ever need to you can always open the AFA case in the future. In the meantime, enjoy your figure and congratulations on your purchase